At first glance, the King Devolution headset looks like a standard 1.5" Chris King headset. What is interesting however, is when you remove the top cap and peer down into the headset, you notice 1.5" bearings. The reducer is the fork race, not the bearing. In essence, you get a 1.5" headset with 1.5" bearings and an 1 1/8" top race/top cap combo and 1 1/8" bottom race - both designed to accept and rotate on 1.5" bearings.
This is an absolute brilliant approach for those riders who want to run a 1 1/8" fork and have a frame that has a 1.5' headtube. Once again the folks at Chris King have wowed us with their awesomeness!